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tube (valve) help

Discussion in 'General Electronics Discussion' started by rematzz, Oct 2, 2015.

  1. rematzz

    rematzz

    41
    1
    Sep 23, 2015
    hi all, i'm restoring a regentone radiogram that isn't playing any sound from the radio and the record player, i have replaced one of the tubes, but it didn't work.

    the only way i can test a tube is with a multi meter, my findings are with the tubes listed, i tested the pins clockwise.

    it has 6 tubes they are:
    ECC85 pins 4+5
    ECH81 pins 4+5
    EF89 pins 1+6
    EABC80 pins 4+5
    EL84 pins 4+5, 1+6
    EZ80 pins 4+5

    does this mean that EF89 needs replacing?
    the EL84 results are from the replacement, does these results mean that its a dud?

    thanks for any help in advance
     
  2. Alec_t

    Alec_t

    2,663
    702
    Jul 7, 2015
    Er, where are the results of your tests?
     
  3. rematzz

    rematzz

    41
    1
    Sep 23, 2015
    where it says pins, with the multi meter the needle went to the max when certain pins where touched with plus and neg of multi meter
     
  4. Minder

    Minder

    2,836
    586
    Apr 24, 2015
    Would appear the audio section is not working so start in the audio output section, a meter lead or touch a probe to the grid should produce a hum or click, especially if you place your finger on the probe.
    Ensure the anode/power +v is present.
    M.
     
  5. duke37

    duke37

    5,213
    718
    Jan 9, 2011
    If you go on vintage-radio.net/forum you can probably get a circuit diagram for £2 which will give the working voltages. Note that these are lethal.
    There is a possibility that the chassis is live, if so it should only be run through an isolating transformer.
    It looks as if it is a standard circuit covering FM, LW and MW.

    EL84, B9A -16
    1. Internal connection
    2.Grid 1
    3.Cathode, grid 3
    4.Heater
    5.Heater
    6 Internal connection
    7.Anode
    8.Internal connection
    9.Grid 2

    If the capacitor feeding the grid is leaky, it could ruin the valve, output transformer and mains transformer. The grid should stay near 0V.
    The cathode, if I remember rightly should be about 7V.
    It is unlikely that the valves are faulty, dodgy switches are much more likely or leaky electrolytic capacitors.

    My method would be to measure the valve voltages and make sure these are somewhere near. It will not work properly if the voltages are wrong.

    EF39, B9A-36
    1. Screen
    2.Grid 1
    3.Cathode
    4.Heater
    5.Heater
    6.Screen
    7.Anode
    8.Grid 2
    9.Grid 3
    There should be a connection between 4 and 5 to drive the heater.

    Best of luck, stay safe.
     
    Last edited: Oct 2, 2015
  6. rematzz

    rematzz

    41
    1
    Sep 23, 2015
    would you say that the ef89 needs replacing because there isn't a connection between the heater pins
     
  7. Alec_t

    Alec_t

    2,663
    702
    Jul 7, 2015
    If the resistance measured between the heater pins (4 and 5) of the EF89 is not less than or equal to about 30 Ohms then the valve is dead.
     
  8. GPG

    GPG

    452
    66
    Sep 18, 2015
    With the valve unplugged
     
  9. GPG

    GPG

    452
    66
    Sep 18, 2015
     
    Last edited: Oct 3, 2015
  10. GPG

    GPG

    452
    66
    Sep 18, 2015
  11. rematzz

    rematzz

    41
    1
    Sep 23, 2015
    thanks everyone for your replies,

    it is a regentone arg 80, on the inside it has the date 27 march 1956
     
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